The invention relates to a cable tensioning installation and a cable tensioning method.
In particular, the invention relates to the field of cable transport installations.
The tension of the cable in a cable transport installation must be kept within a given range to assure that the installation remains safe. However, many conditions affect the tension of the cable, and in particular the vehicle load has a large influence on the tension of the cable. Similarly, the installation operating temperature that can vary between more than 25° C. during the summer and less than −30° C. in the winter has a large influence on the tension of the cable. Finally, creep deformations are applicable to the cable in the long term.
Tensioning stations have to be fitted on cable transport installations to keep the tension of the cable within an optimum range, regardless of the operating conditions of the installation.
In prior art, a pulley over which the cable to be tensioned passes is mounted on a trolley in order to adjust the tension of the cable. This trolley is mounted free to move on a guide rail and is moved by an actuator in the direction required to slacken or tension the cable.
The actuator, for example a jack, has one end fixed relative to the guide rail and the other end is mounted on the trolley so as to move the trolley together with the piston. One description of such an embodiment is given in document FR 2 661 147 in the name of the applicant.
However, this type of tensioning installation occupies a relatively large amount of space in the longitudinal direction relative to the trolley travel distance. Considering the structure of a jack, its stroke is usually only half of its longitudinal dimension when it is extended. Consequently, the segment of rail on which the trolley moves is not more than half as long as the longitudinal dimension of the tensioning installation. Thus, when the cable tensioning installation has to absorb large cable tension variations, it becomes very large.
Thus, these tensioning stations are not satisfactory for applications in which the space available to house the tensioning installation is restricted.